Switched-capacitor amplifiers or amplifiers based on the principle of switching capacitors are based on the principle of switching different paths as loops onto the amplifier in different phases by means of suitable switches and alternately charging capacitors and again providing stored charges. This makes possible a time-discrete signal processing that finds a number of applications, for example, in analog/digital converters and sigma-delta modulators.
Many applications of these amplifiers require a high linearity with simultaneous low offset voltage. It is generally possible to meet these requirements only by using high gain factors, as exhibited by operation amplifiers, for example, and providing appropriate circuits for offset compensation. If it is also required that the amplifier be driven rail-to-rail, however, multistage amplifiers are generally needed.
The requirement profile for switched-capacitor amplifiers in turn places high demands on the stability of the amplifier circuit. The central criterion for circuits with feedback is that, at unity gain, a sufficient phase margin remains so that as a whole the phase is always less than −180°. Any measure that contributes to improved stability of switched-capacitor amplifiers is thus desirable.